1. Field of the Invention
The present invention relates to a multi-chamber system provided with substrate carrier units and, more particularly, it relates to a cassette carrier unit and a substrate carrier unit for positioning a semiconductor wafer or an LCD substrate, for example, and carrying it in the multi-chamber system.
2. Description of the Related Art
As the semiconductor devices are more and more highly integrated, the multi-chamber system has been developed to meet any improvement and change of the process applied to them and continuously process them to shorten their manufacturing course.
when the wafers are re-carried into and out of each of cassette chambers in the multi-chamber system while housing them in a cassette, the cassette is carried from the clean room into the cassette chamber by a cassette carrier unit which is arranged in the cassette chamber. This cassette carrier unit includes a hand, a link arm and an arm drive mechanism.
The conventional cassette carrier unit, however, needs a large space to swing its link arm. The cassette chamber, therefore, must be made large in size to house the cassette carrier unit therein. In addition, an accelerating or decelerating force is added to the cassette carried in and out. This sometimes forces the wafers to come out of the cassette. Damage is thus caused to the wafers.
The multi-chamber system includes an alignment unit for centering the wafer relative to the wafer carrying passageway and directing the orientation flat (which will be hereinafter referred to "ori-fla") of the wafer to a desired direction. The wafer is taken out of the cassette chamber and mounted on a rotary stage of the alignment unit. The alignment of the wafer is conducted on the rotary stage. The wafer is then carried from an alignment chamber to the vacuum process chambers in which it is continuously processed. It is then cooled in a cooling chamber and returned into the cassette.
The multi-chamber system is more advantageous, as compared with the single chamber system, because the wafer transfer and cassette chambers can be made common to the vacuum process chambers. In the case of the multi-chamber system, however, the cassette, alignment and plural vacuum process chambers must be arranged enclosing the wafer transfer chamber. The whole of the multi-chamber system, therefore, becomes large in size. This means that the multi-chamber system occupies a large space in the clean room. It is therefore desired that the multi-chamber system is made smaller in size.